Coil for moving-coil instruments and method of producing the same



June 11, 1968 F. RUEMPELEIN 3,388,

COIL FOR MOVING-COIL INSTRUMENTS AND METHOD OF PRODUCING THE SAME FiledMarch 26, 1965 INVENTOR. FRITZ RUMPELEIN BY I MM .A M

United States Patent Oflice 3,388,329 Patented June 11, 1968 COIL FORMOVING-COIL INSTRUMENTS AND METHOD OF PRODUCING THE SAME FritzRuempelein, Munich, Germany, assignor to Agfa Aktiengesellschaft,Levcrkusen, Germany Filed Mar. 26, 1965, Ser. No. 442,891 Claimspriority, applicgtion 8G6ermany, Apr. 24, 1964,

13 Claims. Ci. 324-154 ABSTRACT OF THE DISCLOSURE The present inventionrelates to coils for electrical measuring instruments, and moreparticularly to improved supporting frames for the convolutions of coilswhich may be utilized in moving-coil instruments of exposure meters forphotographic cameras or the like. The invention also relates to animproved method of producing the frames which are used in such coils.

In accordance with the presently prevailing practice, supporting framesfor use in the coils of moving-coil instruments are produced bysubdividing a hollow cylindrical body into ring-shaped blanks of desiredlength and by thereupon bending the marginal portions of each blankradially outwardly so as to form annular flanges. In a separateoperation, the thus flanged blanks are deformed into frames 'ofrectangular outline and are introduced into a winding machine whichapplies the convolutions of an insulated conductor whereby theconvolutions are held against lateral displacement by circumferentiallycomplete flanges at both axial ends of the frame.

A serious drawback of such methods is that the production of rectangularframes requires too many steps and must be carried out in complicatedand costly machines. Furthermore, and since the ring-shaped blanks areflanged prior to transformation into frames of rectangularcrosssectional outline, the flanges develop jagged edges or serrationswhich are likely to damage the insulation on the conductor or to breakthe wire.

Accordingly, it is an important object of the present invention toprovide a novel and improved method of mass-producing supporting framesfor use in the coils of moving-coil instruments according to which arectangular frame can be produced in a small number of operations but isnevertheless capable of preventing any shifting of convolutions just asreliably as any conventional frame of which I have knowledge at thistime.

Another object of the invention is to provide a method of the justoutlined characteristics according to which all such parts of the framewhich serve to prevent lateral shifting of convolutions in a fullyassembled coil are free of serrations, ragged edges and similarirregularities which might damage or destroy the windings.

A further object of the invention is to provide a method of producingmetallic supporting frames for use in the coils of moving-coilinstruments according to which the frame blank must undergo much lessdeformation than the blank of a frame which is produced in accordancewith the presently prevailing practice but is still capable of properlyretaining and locating the convolutions of a fully assembled coil. t

An additional object of theinvention is to p'rovide a novel rectangularsupporting frame for use in the coil of an electrical moving-coilinstrument.

Another object of the invention is to provide a frame of the justoutlined characteristics which may be massproduced in conventionalmachinery and which may be produced in any desired size to be useful inhighly sensitive as well as in less sensitive electrical measuringinstruments.

A concomitant object of the invention is to provide a coil whichembodies a frame of the above outlined characteristics.

Still another object of the present invention is to provide amoving-coil exposure meter or another electrical measuring instrumentwhich embodies a coil having an improved frame which is produced inaccordance with my method.

Briefly stated, one feature of my invention resides in the provision ofa method of producing a frame for the coil of a moving-coil instrumentor a similar apparatus. The method comprises the steps of forming atubular body of metallic stock and of rectangular cross-sectionaloutline whereby the axial length of the body exceeds the desired axiallength of the frame, severing the body in one or more planes which arenormal to the longitudinal extension thereof to form at least onesleeve-like frame blank having an axial length corresponding to thedesired axial length of the frame and two pairs of opposed flat walls,and deforming one pair of such walls so that each thereof resembles aconcavo-convex (U-shaped) trough with the concave side facing outwardlywhereby the troughs define shallow longitudinally extending channelsadapted to accommodate and to prevent lateral shifting of convolutionsin an insulated conductor which is to be wound around the walls of theresulting frame.

The walls of the other pair may be connected with suitable bearingelements by means of which the coil is installed in a moving-coilinstrument. Such bearing elements may comprise a pair of coaxial arborswhose bases are soldered or otherwise rigidly secured to the inner sidesof the other pair of walls. The length of troughshaped walls ispreferably less than the length of the other pair of walls.

The frame can also support suitable terminals which may be used asconductors of electric current and/or as pointers, and such terminalsmay 'be soldered to the walls of the frame.

The tubular body which is to be severed to yield one or more frameblanks may be produced by upsetting, coldforming, drop-forging or byresorting to any other suitable process.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved coil itself, however, both as to the method of producing itsframe and the method of assembling the same, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of a specific embodiment withreference to the accompanying drawings, in which:

FIG. 1 is aperspective view of a substantially cupshaped tubularmetallic body which is about to be subdivided to yield one or morerectangular frame blanks;

FIG. 2 is a perspective view of a finished frame; and

FIG. 3 is a perspective view of a partly finished coil which embodiesthe frame of FIG. 2.

Referring to the drawings, FIG. 1 illustrates a tubular "body 1consisting of metallic material and having a cross 20. It is clear thatthe bottom Wall 2c is not an essential component of the body 1 and, inthe present instance, has been obtained in response to deformation of abillet by the ram of a press which has penetrated into the cavity of asuitably configurated mold. Thus, and depending on the exact nature ofthe operation which results in the formation of the tubular 'body 1,this body may be open at one or both ends.

In the next step, the body 1 is subdivided to yield one or more frameblanks 4 each of which comprises two pairs of fiat opposed walls 4a, 4band 4c, 4d. The length of the walls 4c, 4d exceeds the length of thewalls 4a, 4b. The planes in which the tubular body 1 is sub divided areindicated by phantom lines 3a, 3b. The frame blank 4 is then insertedinto a press which preferably deforms only the walls 4a, 4b in such away that each of these walls resembles a substantially U-shapedconcavoconvex trough 4a, 4b (see FIG. 2) whose concave side facesoutwardly whereby each of these troughs 4a, 4b defines a longitudinallyextending shallow channel which will accommodate the convolutions of aninsulated condoctor 7 shown in FIG. 3. The directions in Which the walls4a, 4b are deformed to be respectively converted into troughs 4a, 4b areindicated by arrows a shown in FIG. 2.

Prior to convoluting the conductor around the walls 40, 4d and troughs4a, 4b, the inner sides of the walls 40, 4d are connected with the bases5a, 5b of two bearing elements here shown as needle-like arbors 5a, 5bwhich extend into suitable hole jewels (not shown) of a moving-coilinstrument in which the finished frame 4' is put to actual use. Thearbors 5a, 5b are coaxial with each other and their bases 5a, 5b may besoldered to the inner sides of the flat walls 40, 4a.

One or more sheet metal strips 6 may be soldered to the walls of theframe 4' before the conductor 7 is convoluted therearound. Such strips 6may be used as terminals for connection to electric leads and/or aspointers which cooperate With the scale of the moving-coil instrument.

The conductor 7 is convoluted in a suitable winding machine of familiarconstruction, and its convolutions are held against lateral movementbecause portions of each such convolution extend into the channelsbounded by the concave outer sides of the troughs 4a, 4b. When the walls4a, 4b are transformed into troughs 4a, 4b, they undergo as littledeformation as is permissible to still avoid lateral shifting of theconvoluted conductor. At any rate, the deformation of the walls 4a, 4bis substantially less than the deformation of marginal portions inconventional supporting frames wherein such marginal portions must formcircumferentially complete flanges at both axial ends of the frame.Also, and since the troughs 4a, 4b are formed in the last step precedingwinding of the conductor 7, their surfaces remain smooth and cannotdamage or destroy the insulation of the conductor.

It was found that, by using a frame which was produced in accordancewith my present invention, the number of rejects during winding ofconductors 7 is negligible, i.e., the frame is unlikely to damage or todestroy the insulation around the conductor or the wire within theinsulation. Furthermore, and because I start with a tubular body 1 ofrectangular cross-sectional outline, the number of steps necessary tocomplete the production of a frame 4' is considerably less than thenumber of steps needed to produce a flanged frame of conventionaldesign.

Of course, the tubular body 1 of FIG. 1 may be produced in such lengthsthat it yields two, three or a very large number of frame blanks 4.Also, in some instances, I may decide to deform only one of the walls4a, 4b or to deform three or all four Walls of the blank 4.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. An annular one-piece frame of substantially rectangular outline foruse in the coil of a moving-coil instrument or the like, said frameconsisting of metallic sheet material and comprising two pairs ofopposed Walls, the walls of one of said pairs being flat so as tofacilitate attachment of other elements to said flat walls and the wallsof the other pair resembling troughs of concavoconvex outline with theconcave sides facing outwardly so that each such trough defines ashallow longitudinally extending channel adapted to accommodate and toprevent lateral shifting of convolutions in a conductor which is to bewound around said walls.

2. An annular one-piece frame of substantially rectangular outline foruse in the coil of a moving-coil instrument or the like, said frameconsisting of metallic sheet material and comprising two pairs ofopposed walls, the walls of one of said pairs being fiat so as tofacilitate attachment of other elements to said fiat walls and the wallsof the other pair resembling troughs of concavoconvex outline with theconcave sides facing outwardly so that each such trough defines ashallow longitudinally extending channel adapted to accommodate and toprevent lateral shifting of convolutions in a conductor which is to bewound around said walls, and bearing means secured to the inner sides ofsaid one pair of walls.

3. A frame as set forth in claim 2, wherein said bearing means comprisesa pair of coaxial arbors each having a base rigid with one wall of saidone pair.

4. An annular one-piece frame of substantially rectangular outline foruse in the coil of a moving-coil instrument or the like, said frameconsisting of metallic sheet material and comprising two pairs ofopposed walls, the walls of one of said pairs being flat so as tofacilitate attachment of other elements to said flat walls and the Wallsof the other pair resembling troughs of concavoconvex outline with theconcave sides facing outwardly so that each such trough defines ashallow longitudinally extending channel adapted to accommodate and toprevent lateral shifting of convolutions in a conductor which is to bewound around said walls, and a pointer fixedly secured to one of saidwalls. a

5. A frame as set forth in claim 4, wherein said pointer is rigid withone wall of said one pair of walls.

6. An annular one-piece frame of substantially rectangular outline foruse in the coil of a moving-coil instrument or the like, said frameconsisting of metallic sheet material and comprising two pairs ofopposed walls, the walls of one of said pairs being fiat so as tofacilitate attachment of other elements to said flat walls and the wallsof the other pair resembling troughs of U-shaped cross section havingconcave sides facing outwardly so that each such trough defines ashallow longitudinally extending channel adapted to accommodate and toprevent lateral shifting of convolutions in a conductor which is to bewound around said walls.

7. A coil for moving-coil instruments or the like, comprising an annularone-piece frame of substantially rectangular outline and consisting ofcomparatively thin metallic sheet material, said frame including twopairs of opposed walls, the walls of one of said pairs beingsubstantially fiat so as to facilitate attachment of other elements tosaid fiat walls and the walls of the other pair resembling troughs ofU-shaped cross section having outwardly facing concave sides so thateach such trough defines a shallow longitudinally extending channel; anda series of convolutions of an electrical conductor surrounding saidwalls and having portions accommodated in said channels whereby thewalls of said other pair prevent lateral shiftiug of such convolutions.

8. A coil as set forth in claim 7, wherein the length of the walls ofsaid one pair exceeds the length of said trough-shaped walls.

9. A method of producing a one-piece frame for use in the coil of amoving-coil instrument or the like, comprising the steps of forming asleeve-like blank of rectangular outline having two pairs of opposedfiat walls; and deforming only one pair of such fiat walls into theshape of a concavo-convex trough with the concave side facing outwardlyso that the walls of said one pair define shallow longitudinallyextending channels adapted to accommodate and to prevent lateralshifting of convolutions in a conductor which is to be wound around theresulting frame while the walls of the other pair of walls remain fiatand therefore can be easily connected to other elements.

10. A method of producing a one-piece frame for use in the coil of amoving-coil instrument or the like, comprising the steps of forming atubular body of rectangular cross-sectional outline whose axial lengthexceeds the desired axial length of the frame; severing said body inplanes which are normal to the longitudinal extension thereof to form atleast one sleeve-like frame blank of rectangular outline having twopairs of opposed fiat walls and an axial length corresponding to thedesired axial length of the frame; and deforming only one pair of suchflat walls into the shape of a concave-convex trough with the concaveside facing outwardly so that the walls of said one pair define shallowlongitudinally extending channels adapted to accommodate and to preventlateral shifting of convolutions in a conductor which is to be woundaround the resulting frame while the walls of the other pair of wallsremain fiat and therefore can be easily connected to other elements.

11. A method of producing a one-piece supporting frame for use in thecoil of a moving-coil instrument or the like, comprising the steps offorming a tubular metallic body of rectangular cross-sectional outlinewhose axial length exceeds the desired axial length of a frame; severingsaid body in a plurality of parallel planes to subdivide the same into aplurality of frame blanks whose axial length corresponds to the axiallength of a finished frame and each of which comprises two pairs ofopposed fiat walls; and deforming only one pair of walls on each of saidblanks into the shape of U-shaped troughs having outwardly facingconcave sides so that each trough defines a shallow longitudinallyextending channel bounded by smooth surfaces adapted to accommodate andto prevent lateral shifting of convolutions in a conductor which is tobe wound around the walls of the resulting frame to form therewith afinished coil while the walls of the other pair of walls remain flat andtherefore can be easily connected to other elements.

12. A method of producing a one-piece supporting frame for use in thecoil of a moving-coil instrument or the like, comprising the steps offorming a sleeve-like frame blank of rectangular outline having twopairs of opposed flat walls; deforming only one pair of said walls intothe shape of a concavo-convex trough with the concave side facingoutwardly so that such troughs define shallow longitudinally extendingchannels adapted to accommodate and to prevent lateral shifting ofconvolutions in a conductor which is to be wound around said walls toform therewith a coil while the walls of the other pair of walls remainflat; and attaching a bearing element to the inner side of each of saidfiat walls of said other pair of walls.

13. A method as set forth in claim 12, wherein said bearing elements aresoldered to the respective flat walls.

References Cited UNITED STATES PATENTS 985,420 2/1911 Keller 3362231,825,105 9/1931 Terman 336208 2,755,821 7/1956 Stahl 242-118 FOREIGNPATENTS 915,715 7/1954 Germany. 264,993 1929 Italy.

LARAMIE E. ASKIN, Primary Examiner.

T. J. KOZMA, Assistant Examiner.

